Tracking systems are required for stabilizing images of distant targets or mobiles on a detector sensor, and for enabling stable contact to be established over an extended period of time. Such optoelectronic systems apply, in particular, to laser communications systems between satellites, to docking sensors for use in a docking operation in space, to pointing systems for telescopes or for interferometer elements as used in astronomy, and also to missile homing systems.
Such tracking systems include a tracking sensor constituted by a matrix of individual photoelectrical sensors for comparing the intensities of light signals received at a plurality of points regularly spaced around the axis of the beam which is being tracked.
It is also known to use a semitransparent mirror to take a fraction of the intensity of the beam that is focused on the tracking sensor, with the light transmitted by the semitransparent mirror being focused on the photoelectrical sensor of the detector. As explained below with reference to FIG. 1, devices of that type become misadjusted very often, in particular because of thermal expansion.
Semiconductor chips are also known that include a photoelectrical sensor or detector surrounded by an annular tracking sensor constituted by four elementary photoelectrical sensors. As explained below with reference to FIG. 2, such an implementation is unsuitable for selecting different magnifications for the detector sensor and for the tracking sensor. In addition, it presents a dead field between the fields of view of the detector sensor and of the tracking sensor.